The present invention relates to electronics assemblies, and is primarily concerned with thermal management therein. Many such assemblies will be located in racks for housing in for example nineteen inch cabinets, or other size cabinets, in cabinets such as twenty three inch or metric cabinets. The assemblies may for instance be employed as servers for a number of systems, for example in local area networks (LANs), wide area networks (WANs), telecommunications systems or other operations such as database management or as internet servers.
Such an assembly will typically comprise a supporting chassis that houses a motherboard or backplane and a number of daughterboards or module cards that extend in planes generally perpendicular to the plane of the motherboard. Because of the amount of heat that is generated during operation of the equipment and the thermal sensitivity of the equipment, it is necessary to provide cooling fans in order to direct a current of air through the assembly or otherwise permanent damage would occur.
One form of assembly includes so-called “RAS computers” that is to say, computers that need to provide a high degree of reliability, availability and serviceability, and which therefore need to maximise the length of time during which the computer is operational. If a computer cannot run with a failed fan, its reliability is compromised, and if it must be shut down to replace the fan, the availability (uptime) of the system will be compromised. The fan serviceability, including typical time to replace and special tool requirements can also contribute to the system availability by affecting the probability of repair success.